The objective of this proposal is to characterize the essential characteristics, and role of, mammalian, adult- born olfactory bulb interneurons derived from the subventricular zone stem cell niche. Therefore, two specific aims have been developed to determine if early-born interneurons differ from those generated in the adult, and to determine the influence of activity on the differentiation of adult-derived interneurons. Specific Aim 1: In order to determine whether olfactory bulb interneurons differentiating during embryonic and perinatal neuronal development are different from those derived from adult neuronal precursors, genetic fate-mapping experiments will be performed. Specific Aim 2: To characterize the influence of activity on adult-derived olfactory bulb interneurons, interneuron morphology, gene expression, and survival will be assessedfollowing genetic ablation of activity. These experiments will contribute important information regarding the significance and contribution of adult neurogenesis to the function of the mature animal. In addition, information regarding the mechanism of neuronal differentiation in the adult will aid in efforts to guide that differentiation toward nervoussystem repair following disease or injury.